Screen filters are well-known in the art for filtering out solids from liquids such as water for irrigation purposes and similar applications requiring filtration. Screen filters cleanse the liquids having solid contaminants entrained therein by depositing the solids on the screening of the filter while conveying the cleansed water through the screen and out of the filter housing. The screen filters that are known in the art have many different configurations but are basically classified on the basis of the liquid flow through the filter, i.e., the flow of the liquid from the inside of the screening to the outside of the screening or the flow of the liquid to be filtered from the outside of the screening to the inside thereof. When a screen filter is constructed and defined to cause the liquids to flow from the inside out, raw water or contaminated liquids enter the interior of a screen housing, passes through the screening longitudinally of the housing, and the filtered water exits along the housing body at each of the apertures for the screening and out the discharge port of the filter housing. The support structure for the screened material is the inside of some type of cylinder or the cylinder itself is the screen. When the liquid filter is defined so that the contaminated water flows from the outside of the screening, then, the raw water or liquid enters the screening along the housing body longitudinally and passes through the apertures of the screening longitudinally along the outside of the screen cartridge. The filtered water exits along the interior of the screen cartridge and out of the filter housing. The support structure for the screen cartridge is the outside of some type of cylinder or the cylinder itself is the screen. It is also well-known to filter contaminated liquids such as water with the use of sand filters which trap the contaminants within the sand filtration media, rather than by the screening, in the same general fashion as the screen filters.
When a screen filter is resorted to, the contaminants or solids lodge in or are deposited on the screen cartridge, making it necessary to clean the screening from time to time to maintain the efficiency of the filtration. Various methods are presently known for cleaning the screen filters, including the method of physically removing the screen element from its housing and physically cleaning it by conventional flushing. A second method is known as the through flushing method in which the raw water is passed through the screen cartridge for removing the particulate material from the screening material. A further method is to backwash the filter by admitting filtered water at the outlet port and forcing it back through the screening toward the raw water or the inlet side of the filter. In this method the contaminants flow out the inlet port through appropriate valving. Accordingly, there is a present need for an improved screen filtration structure and methods of cleaning the filter and preferably for providing a rupture free screen for filtration and cleansing purposes that minimize the amount of liquid and time required for cleaning of the filters.